How do I make this concave shape?
Welcome on the forums, to get you started...
I used a modifier to spiral a curve line
next added a modifier to make it solid
next added 4 cylinders by mirroring one.
next i did a boolean operation to subtract the 4 cylinders.
for visibility i altered the 4 cylinders so you see them as wire frame.

Note you can change this file, the modifiers, or in edit mode change the curve or the cylinders.